Interlocking system for railroads



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Dec. 9, 1941. A. LANGDON INTERLOCKING SYSTEM FOR RAILROADS- Filed Jan. 8, 1937 8 Sheets-Sheet 4 INVENTO ATTOiQNEY Dec. 9, 1941. A. LANGDON INTERLOCKING SYSTEM FbR RAILROADS 8 Sheets-Sheet 5 u vv TL 1. lllllllllll I 3 mmmg EL fin UGO u km 10' I0 Dec. 9, 1941. A. LANGDON INTERLOCKING SYSTEM FOR RAILROADS Filed Jan. 8, 1937 8 Sheets-Sheet 6 3 8:23 2 n s T mvsw 2: E

Dec. 9, 1941. A. LANGDON INTERLOCKING SYSTEM FOR RAILROADS Filed Jan. 8, 1937 8 Sheets-Sheet 7 Dec. 9, 1941. A. LANGDON INTERLOCKING SYSTEM FOR RAILROADS Filed Jan. 8, 1937 8 Sheets-Sheet 8 28:95 was muzutkn xudt. :s o eu.&E. ts 2 9m 9 fit m 95.6 29:6 5; Bt u xz 339 e $5 955 we co dpomo w m Tv m 8 Bh ukz omo L INVEflNT ATTO'RNEY Patented Dec. 9, 1941 l INTERLOCKING SYSTEM FOR RAILROADS Andrew Langdon, Brighton, N. Y., assignor to General Railway Signal Company, Rochester,

Application January 8, 1937, Serial No. 119,641

67 Claims.

This invention relates to switch and signal control systems for railroads, and more particularly to systems of the so-called entrance-exit type in which the track switches in any given route are collectively operated to the appropriate positions to establish that route and a signal is cleared for governing train movement over that route by manipulation of manual control devices to designate merely the entrance and exit ends of that route.

In such an entrance-exit type of switch and signal control system, freely movable manual control devices in a form of small buttons or the like, are provided for each signal location of the track layout constituting an entrance and/or exit end of some route or routes afforded by the track layout. In the present embodiment, an entrance signal location may be designated by turning a small knob or button conveniently termed an entrance button; while an exit signal location may be designated by pressing a small push button, conveniently termed an exit button. However, any other suitable arrangement of movable elements may be employed to operate electric contacts for performing distinctive entrance and exit functions in accordance with the operators manipulation. These manual control devices are mounted on a control panel within convenient reach of an operator, and are suitably identified with their respective signal locations by reason of their location on the control panel adjacent points on a miniature track diagram of the track layout corresponding with their respective signals.

Generally speaking, any one of the various forms of track layouts used on railroads may be considered as made up of one or more groups of switch points in the form of single switches, cross-overs, or the like, which interconnect various stretches of track, each of such groups providing a plurality of routes extending from an entrance signal location, which signal must be cleared to permit a train to enter the route, over one or more track switches of the group in certain normal or reverse positions, to a point on the track constituting the exit end of such route, which exit point may be the entrance end of some other route or routes in an adjoining group, or in some cases may be the end of the territory under the control of the operator. afforded by such a group of associated switches may be conflicting routes, namely, routes which cannot be used for train movement at the same time; while some of these routes may be non- Some of the routes up and used at the same time. Since the operation of track switches which may be involved in conflicting and non-conflicting routes is subject to some suitable form of interlocking control, so as to prevent setting up conflicting routes, agroup of switches associated with stretches of track to provide these various conflicting and non confiicting routes may be said to constitute an interlocked group.

Each of the various routes aiiorded by an interlocked group may be used for train movement in one direction or in both directions, as may be required for the desired movement of trafiic. For train movement over a route in one direction, an entrance signal is provided and located adjacent the entrance end; and for train movement in both directions over a route, there is an entrance signal for each end of that route. If the track layout includes two or more interlocked groups located end-to-end, the signal locations at the adjoining ends of any two interlocked groups are each in effect an entrance signal location for one interlocked group and an exit signal location for the other interlocked group. These signal locations may for convenience be termed intermediate signal locations with respect to through routes that may be provided through such adjoining interlocked groups.

More specifically, when a track layout includes two or more interlocked groups, there may be certain routes of these interlocked groups which may be set up at the same time in an end-to-end relation, so to speak, and provide what is conveniently termed a through route" over two or more successive interlocked groups and past one or more inwrmediate entrance signal locations.

Although such a through route can be established by entrance-exit manipulation for each in terlocked group in turn, one object of the present invention is to provide that the system will set up a through route in response to the operator's manipulation of the manual control devices to designate the extreme entrance and exit signal locations of the desired through route. The system automatically acts in response to such manipulation to establish the proper route over each of the interlocked groups as required to provide the through route, and cause the intermediate entrance signals for such through route to be automatically cleared. Obviously, such operation of the system greatly simplifies and facilitates the operators manipulation for the control of trafiic through the interlocking plant.

In some track layouts, the arrangement of conflicting routes, that is, routes that can be set 55 switches and stretches of track for any given in terlocked group may be such that there are two or more alternative or optional routes between the same common entrance and exit signal locations of that interlocked group. Under some conditions, either one of these alternative routes may be used for train movement, but under other conditions a route may be set up in conflict with one of the alternative routes so that the other alternative route is the only one available for use. Thus, another object of the invention is to provide a system that acts when the operator manipulates the buttons for common entrance and exit signal locations for these alternative routes to automatically select the alternative routes one at a time in some predetermined order of preference and dependent upon whether or not the respective routes can be established.

.A similar problem of alternative routes is also presented in connection with the establishment of through routes, that is, when a plurality of interlocked groups are located end-to-end, the track layout usually afiords two or-more alternative routes between the same entrance and exit signal locations of difierent interlocked groups, thus providing what may be termed alternative through routes. While the number of alternative through routes depends upon the number of optional or alternative routes in the respective interlocked groups, there may be alternative through routes even though there are no alternative or optional routes in any of the interlocked groups involved.

Under some conditions all of the alternative through routes between entrance and exit signal locations of different interlocked groups may be available for use without any conflict with other established routes; and under other conditions some one or more of the alternative through routes'may be in conflict with some route established in some one of the interlocked groups involved. Also, some of the alternative through routesthat may be afforded by the track layout are not desirable for use, as for example, a runaround movement from one track over a crossover in the reverse position to another track and then back to the first track over another crossover in the reverse position, when train movement straight along the first track is possible.

Where the track layout afiords alternative through routes, the present invention provides that only one of the various alternative through routes will be selected and established upon actuation of manual control devices to designate the extreme entrance and exit ends thereof; and since one or more of these alternative routes may not be available or desirable for use at different times, this selection of a particular through route to be established is in accordance with some order of preference and is also dependent upon conditions of conflict with some other through route or route over some one of the same individual interlocked groups.

In accordance with this invention, the operation of the system to establish routes and clear signals under these various conditions is initiated or controlled by actuation of freely movable manual control devices to designate first an entrance signal location of the track layout where the train to be moved is approaching or standing, and then an exit signal location of the track layout to which it is desired to move the train. Since these manual control devices are freely movable and may be actuated by the operator at any time, safe operation of the system requires that the power operation of all track switches should be subject at all times to the control of track circuits and associated relay means for detector or route looking, so that the operation of each of the switches in a route is prevented while a train is passing over or approaching said switches in traversing the route, in spite of any control that may be imposed by the operator carelessly or by mistake to change the position of such switch point.

Also, the signal to be cleared should be the one at the entrance signal location designated by the operators manipulation, and this signal should not clear unless all of the switches in the route have been properly operated to the required position. The same signal, perhaps with distinctive route or speed indications, is ordinarily used to govern train movement into a plurality of difierent routes; and since this signal should not assume its clear condition unless the switches have been operated to the position required for a particular one of these routes than designated by the operator, according to this invention, each signal is cleared by closing a clearing circuit which is closed only if all of the switches in some route originating at the corresponding entrance signal location are in the normal or reverse positions corresponding with the control then being exercised by the operator. It is also considered preferable to arrange the signal clearing circuits so that a signal may not clear for a route until all of the switches in that route are effectively locked against power operation.

In connection with the control of signals by track circuits, it is contemplated that the practice suitable for the particular layout and kind of traffic will be adopted. In the case of some signals, such as those governing high speed train movement, the signal clearing circuit would ordinarily be controlled by track circuits of a portion of track extending to the next succeeding signal governing train movement in the same direction, in accordance with the principles of automatic block signalling, so that such a signal may not assume its clear condition unless the block ahead is not occupied by some other car or train. Under other conditions, particularly where it is desirable to move a locomotive or train into an occupied section of track for coupling or uncoupling of cars, or for switching moves, the signal may be allowed to clear independently of the track circuits, provided the switch points are in their full normal or reverse positions and safe for train movement. Such variations in the kind of signal control in accordance with recognized practice are not material to the invention; and while various arrangements of high speed signals, shunt or dwarf signals, or call-on signals may be employed, in the interests of simplicity it has been assumed in connection with the particular embodiment of the invention illustrated that the entrance signals for the various routes will be of the low speed type Without automatic track circuit control.

In its broad aspect, this invention involves a rather complex combination or organization of electrical relays, circuits, and contacts, which are adapted and arranged for each installation to conform with the location and arrangement of switches, signals and the like. Generally speaking, in addition to suitable means for safeguarding the power operation of switches and the clearing of signals under the supervisory manual. control of the operator, the system comprises an organization of relays, circuits, and contacts, constituting what may be conveniently termed a route selecting or establishing means, which is conditioned and operated by the actuation of manual control devices to designate the entrance and exit signal locations of a track layout, and which acts automatically to control the power operation of the appropriate switch points to the proper positions to provide a route, or a through route, between any entrance and exit signal locations designated, and to control the clearing of the signal or signals of such a route or through route, regardless of the number of alternative routes or alternative through routes that may be afforded by the track layout, and with the due regard to conflict with other routes then established by the route establishing means.

One characteristic feature of this route establishing means is that the power operation of each of the switches to the normal or reverse position is governed by the energization of associated normal and reverse switch control relays; and an assemblage of circuit paths and contacts each relating to and controlling the energization of the switch control relays for one of the several individual switches are organized in such a way that actuation of manual control devices to designate the entrance and exit ends of any given route will cause energization of a selected switch control relay for each of certain selected switches, as may be required to operate the appropriate switches to the proper positions to provide such a route, these circuits having their interconnections and continuity governed by contacts of these switch control relays so as to provide the necessary interlock between conflicting routes. In this arrangement characterizing this invention, the routes are established and the interlocking between conflicting routes is effective by reason of operations relating to the switches individually, rather than by reason of operations relating to the respective routes as a whole.

Another important aspect of this invention is that the desired and appropriate route is provided or built up by what may be termed preselection and completion operations of the route establishing means, for the purpose of enabling one appropriate route through an interlocked group, or a through route over a plurality of interlocked groups, to be automatically selected and established efiectively upon actuation of manual control devices to designate the entrance and exit ends of such route or through route.

Considering the principles underlying this scheme for establishing routes by pre-selection and completion, any one of the various routes of a railway track layout may be analyzed as including one or more single switches, ends of crossovers, or the like, over which a train moves in turn in traversing the route, each of these switches having its points disposed with respect to the entrance end of the route, either in a facing point relation and capable of diverting train movement from the route in question to some other route, or in a trailing point relation so as to have only one position suitable for continued train movement in a direction away from said entrance signal location. Upon further analysis, it can be seen that switches in a route in a facing point relation to the entrance end are necessarily in a trailing point relation to the exit end. In short, any route may be considered as made up of switches disposed in a trailing relation to one end of the other end of the route. Accordingly, it can be seen that any particular route of an interlocked group when identified by its entrance and exit ends, can be selected from all of the other routes by combining the position of switches in turn, starting at the exit end, in accordance with the position thereof required by reason of their trailing relation to either the entrance or exit end, as the case may be. In other words, when the trailed positions of switches for one direction of train movement from one signal location are combined with the trailed position of switches for the other direction of train movement from another signal location, the result is a route between said signal locations.

With these considerations in mind, pre-selection according to this invention may be said to involve, in response to the actuation of a manual control device to designate any given entrance signal location, the operation of automatically pre-selecting or conditioning each of those switches which is included in any one of the routes originating at said entrance signal location and is disposed in trailing relation thereto, for operation to the position required on account of such trailing relation. In this connection, although a route is not identified until the exit end as well as the entrance end has been designated, once an entrance signal location is designated, there is a determination of the position to which the trailed switches in all of the possible routes from the entrance signal location should be operated, if such operation is required for the particular one of these routes subsequently chosen, inasmuch as the only possible paths for tram movement, regardless of which of these routes will be chosen, will be over these trailed switches in certain positions.

During this pre-selection operation, the trailed switches will not be actually operated by energization of their switch control relays, but the route establishing means is conditioned or prepared to cause operation of such of these switches as may be necessary when the particular route to be established is identified by designation of its exit end. This pre-selection operation in effect selects energizing circuits for the switchcontrol relays associated with these trailed switches, so as to provide for the energization of the proper switch control relays when the completion operation occurs.

Further, the system is arranged so that the pre-selection just explained is effective with respect to each of the trailed switches only if a path for train movement from the designated entrance signal location to and over said switch in the pre-selected position is establishable, i. e. is not in conflict with some route then established by the route establishing means. Consequently, if switches have been pre-selected for operation to the normal position, for example, preparatory to a completion operation about to be described, it is assured that a path for train movement over these switches in the normal position and extending to the designated entrance signal location can be established.

Following this pre-selection operation, the completion operation of the route establishing means occurs when a particular one of the routes originating at the designated entrance signal location is identified by the actuation of a manual control device to designate its exit end. During this completion operation, the proper switch control relays of the appropriate switches required for this route are energized by an operation which may be explained in general terms as involving determination of the position of successive switches in turn, starting with the switch nearest the exit end, dependent upon the trailing relation of these switches to the respective entrance and exit ends, the switches remote from the exit end to have their position thus determined being selected in accordance with the position of the next adjacent switch nearest the exit end. In the case of switches in a trailing relation to the entrance end of the route, the position to which they are operated is in accordance with the pre-selection; and in the case of the other remaining switches in the route the position to which they are operated is in accordance with that required by reason of their trailingrelation to the exit end of the route. The completion operation to establish a particular route originating at the designated entrance sigi nal location renders ineffective the pre-selection with respect to all trailed switches involved in all other routes originating at the same entrance signal location; but this does not prevent subsequent preselection of one or more of these same switches upon designation of some other entrance signal location for a, non-conflicting route.

Since routes are established by a completion operation following a pro-selection operation, the proper functioning of the system requires that the manual control device be manipulated to designate an entrance signal location first and then an exit signal location; and in order that an accidental or careless manipulation by an operator may not cause unnecessary or abnormal operation of switches, provision is made in accordance with this invention so that the actuation of a manual control device to designate an exit signal location is not effective to exercise any control upon the route establishing means, unless some other manual control device to designate an entrance signal location had been previously actuated to perform the desired preselection operation. Under some conditions a route between a designated entrance and exit signal location may be in conflict with some route then established; and provision is also preferably made in accordance with this invention so that the actuation of a manual control device to designate an exit signal location is not effective to control the route establishing means, unless some route to that exit signal location is not inconflict with any established route, in order to avoid unnecessary operation of switches for routes that cannot be established.

In the specific embodiment of the invention illustrated, the pre-selection functions are performed by what is conveniently termed a selfselecting initiating circuit network; and the completion functions are performed by a completion circuit network. The detail features and operation of pre-selection and completion as exemplified by these initiating and completion circuit networks are more conveniently discussed as the circuits and operation are described in de- 5 tail. 1

This general scheme of pre-selection and completion is specially adapted to provide the desired control for the automatic selection of optional or alternative routes. When, for example, that end of a crossover, which is in a trailing relation to a designated entrance signal location, is required to be in opposite positions for different alternative routes, the pre-selection is arranged to be normall effective for a preferred one of these positions only, as for example, the normal position. Consequently, if the common exit signal location of alternative routes should be designated, this crossover is positioned during the completion operation to provide a predetermined one of the alternative routes. Also, this pro-selection operation for the preferred position of such switches involves the energization of circuits having their continuity controlled by contacts of switch control relays in such a way that the pre-selection is not effective with respect to any given one of the switches unless part of a route or path for train movement from the designated entrance signal location to and over said given switch in the pre-selected position is not in conflict with some route then established by the route establishing means. Thus, if the predetermined or preferred position cannot be used on account of conflict with some established route, the other position of such switch is preselected, and during the completion operation another alternative route is the one that is established.

The principle of pre-selection and completion is also specially adapted for through route operation. In accordance with this invention, upon actuation of a manual control device to designate any given entrance signal location, the pre-selection is efiective for all routes originating at that signal location in all interlocked groups; and when the extreme exit end of a through route has been designated, a particular route is established through the corresponding remote interlocked group in accordance with the preselection to provide a route through that remote interlocked group from a particular intermediate entrance signal location. Upon completion of this route through the remote interlocked group, suitable relay means and circuit connections for through route operation are rendered effective at this particular intermediate signal location to perform entrance and exit functions at that signal location, much the same as if the manual control devices had been actuated for that signal location. This controls the clearing of the signal at the intermediate signal location in question, and also initiates a completion operation for the next adjoining interlocked group, which establishes a particular route through that interlocked group to a particular intermediate entrance signal location of that group: and this same plan of operation is repeated for as many interlocked groups as may be necessary until the complete through route is established and the signals controlled to assume the clear condition.

During such preselection operation in the different interlocked groups, each of the switches in a trailing relation to the designated entrance signal location is pre-selected for operation to a position to conform with some route originating at that entrance signal location, provided routes or parts of routes forming a path for train movement from that signal location to and over said switch in said selected position is not in conflict with some other established route. Consequently, the completion operation is effective to select automatically between alternative through routes that may exist, in accordance with a predetermined preference and dependent upon conflict with other established routes, in a manner which can be understood to better advantage as the detail operation is explained.

A further important attribute of this invention is the economy in the number of relays required to perform the functions of preselection, completion, and the like in the rather involved organization constituting the invention; and in general the number of relays required is dependent upon the number of switch points in the track layout, and not upon the arrangement of these switch points, or the number of routes aiforded by the track layout. In the preferred embodiment of the invention illustrated, there is a preselecting relay, a normal and a reverse switch control relay for each single switch; and a preselecting relay and normal switch control relay for each end of a crossover, with a reverse switch control relay common to both ends of a crossover.

Another feature of the invention is that the auxiliary or emergency switch levers, which are usually provided in an entrance-exit system for controlling the operation of switch points individually, controls the energization of the switch control relays in such a way that the operation of an auxiliary lever is not effective to interfere with a route established, but may be used to modify the operation of the route establishing means, if occasion should require.

Other objects, purposes and characteristic features of the present invention will be in part obvious from the accompanying drawings, and in part pointed out as the description of the invention progresses.

In describing the invention in detail, reference will be made to the accompanying drawings, in which like letters in the reference characters designate similar functions or relationships with the distinctiveness between such reference characters provided by the use of distinctive preceding numerals; in which like preceding numerals in the reference characters when applied to different letters represent the inclusion of such devices within a particular group; and in which:

Figs. 1, 2, 3 and 4, when placed end to end, show the miniature track diagram and self-selecting networks for a complicated tracklayout involving the feature of end-to-end entranceexit control;

Fig. 5 shows typical. switch and signal control circuits, which are governed by a self-selecting network, and their relationship to various ofthe automatic traihc controlling features.

Figs. 6, '7 and 8 show the track layout and signal control employed. in connection withthe endto-end feature shown in Figs. 1, 2, 3 and. 4-;

Figs, 1 and 4, when placed end to and disclose the miniature track diagram and self-selecting network for a single interlocked group; and

Figs. 6 and 8, when placed end to end, show the track layout and signal control for a single interlocked group as shown by Figs. 1 and 4.

Fig. 9 illustrates the relationships of the various figures.

For the purpose of simplifying the illustration and. facilitating in the explanation thereof,- the conventional parts and circuits constituting, the embodiment of the invention have been shown diagrammatically and certain conventional illustrations have been employed, the drawings having" been made more with the idea of making clear the purposes and principles of the present invention together with its mode of operation, than with the idea of illustrating the specific construction and arrangement of parts that would probably be employed in practice:

Th various relays and their contacts are illus trated in a conventional manner and symbols are employed to indicate'connections to theterminals of batteries or other suitable sources of electric current suppl instead of showing all-of the Wir ingfconnectings to such terminals.

The symbols and are employed to indicate the positive and negative terminals respectively of suitable batteries or other sources of electric energy; and those terminals with which these symbols are used are assumed to have current flowing from the positive terminal designated to the negative terminal designated j z The symbols employed with any one circuit are considered todesignate the terminals of the same battery or other suitable source, but it is to be understood that as many separate sources maybe provided as found necessary, or as many sources may be combined into a single source as found expedient in the practice of the invention.

If alternating current is employed, the symhols should be considered to represent the instantaneous relative polarities of the respective terminals.

Where groups of devices are referred to in a general way, such devices will be designated by the letters or preceding numerals characteristic of such groups instead of mentioning each specific'reference character of that group of devices.

Apparatus In the operation of railways, track switches are employed at junctions, stations, terminals, shunting yards, and the like, for directing train movement from one track to another, in and out of platforms, sldings, and the like, so as to provide efiicient and expeditious movement of traffic; and the tracklayouts for the varying conditions of traffic movement involve widely varying arrangements of tracks and switches. The system of this invention is organized so that, by the approprlate selection and inter-connection of parts, it" may be applied to any one of these various track layouts; and the particular track layout illustrated. and used as a basis for an illustration of the features, functions, and mode of operation of this invention, is merely typicalfior representative. Accordingly, the various terms and expressions used herein with reference to this typical track layout are intended to be employed in a sense applicable to the various other arrangements of track switches and signals that may be encountered in practice.

For the purpose of disclosin the invention as applied to two interlocked groups, a track layout is" employed as shown by the placing of Figs. 6, 7 and 8 end to end. In order that the invention may also be considered in its simplest form, that is; a form which employs only a single" interlocked group, the drawings have been arranged so that the placing of Figs. 6 and 8 end to end provide a track layout for such a single interlocked: group.

It is therefore thought expedient to set forth the apparatus used with the track layout of the combined Figs. 6, 7 and 8 as well as the organization' of the complete system for such a track layout, although in the consideration of the operation of the system of the present invention it is considered expedient to first describe the operation of the system for a single interlocked group.

Track layout-With reference to the combined- Figs. 6, '7 and 8, the invention has been shown applied to a track layout including a stretch of double track connected by the crossovers including the track switches 2TSA 2TSB, 4TSA TS-B, 5TSA 5TSB, 'ITSA 'FTSB, 9TSA9TSB, I'BFSAIBTSB-, aswell as including the track switches 3T8, ETS, BTS, and HTS connecting turnout tracks to the double tracks. Signals IOI, I02, I03 and I04 are provided for governing east bound traffic at the west entrance to the track layout, while signals I08 and I09 are provided for governing west bound traffic at the east entrance to the track layout. Signals I95, I06 and Ill! are provided at an intermediate point in the track layout for governing east bound traflic, while signals H and, III are provided at an intermediate point in the track layout for governing west bound tralfic.

1 Inasmuch as the opposite ends of a crossover are usually operated at the same time, each crossover may be considered as operated by a single switch machine SM, although it is to be understood that two such switch machines may be employedfor each crossover if so desired, all within the scope of the present invention. Thus, the switch machines ZSM, 35M, lSM, SM, BSM, ISM, 8SM, HSM, lllSM and IISM have been shown for the crossovers and track switches, which switch machines may be of any suitable type, such, for example, as disclosed in the patent to W. K. Howe, Pat. No. 1,466,903, dated September 4, 1923, having their motors controlled in any suitable way such as shown, for example, in the patent to W. H. Hoppe et al. Pat. No. 1,877,876 dated September 20, 1932. If the control of the Hoppe et al. patent is used, relay WZ of this disclosure is assumed to control the application of One polarity or the other to the control relay CR of such patent.

The various signals are assumed to be color lightsignals giving the usual indications of green for clear and red for danger or stop, and yellow, if an added indication is desired for caution, when track circuit control is employed. However, these signals may be of the search light type, the semaphore type, or any other suitable type instead of the particular type chosen for the embodiment of the present invention.

The track layout has been shown divided into track circuits separated by suitable insulated joints. These track circuits are provided with the usual track batteries and track relays, of which track relays IZT, I3T, MT, I5T, IBT, IIT, I8T and [ST have been shown. The number of track circuits has been determined in accordance with the usual principles by providing at least one track circuit for each parallel or nonconfiicting route in a particular interlocked group. These normally energized track circuits are wired in the usual manner to provide for fouling protection and to provide for the insulation of the track switches, such details of wiring having been omitted for the sake of simplicity in the disclosure.

Each' track switch and crossover is provided with the usual switch position repeating relay WP of the usual polar-neutral type. Each relay WP is energized with one polarity or the other in accordance with the normal or reverse locked positions of its track switch in correspondence with its switch machine SM, and is deenergized whenever its track switch or crossover is unlocked or is in operation. The polarized circuit for controlling such a switch position relay is governed through the medium of a point detector contact mechanism for each track switch such as shown for example in the patent to S. S.

Bushnell, Patent No. 1,517,236, dated November witch; machines SM were employed for a crossover, which mechanisms would jointly control the polarized circuit for the single switch position repeatin relay WP for such crossover.

Control machine-A suitable control machine is located in the central oihce and is provided with a control panel on which a track diagram is constructed in a manner to be representative of the actual track layout in the field (see Figs. 1, 2, 3 and 4). The construction of this track diagram may be of any suitable type, such for example, as described in the prior application of S. N. Wight, Ser. No. 69,905, filed March 30, 19 36, or as shown in the prior application of F. B. Hitchcock, Ser. No. 74,709, filed April 16, 1936. The features of the control panel for indicating the routes set up, track occupancy conditions and the clear or stop condition of the signals, may be provided in any suitable manner, the present invention being more particularly concerned with the setting up of the routes and the interlocking between such routes.

At points on the miniature track layout representative of the route ends on the actual track layout in the field, are located suitable entrance and exit buttons which control the setting up of routes and the clearing of signals for such routes. More specifically, an entrance button NB is provided for each of the signal locations, such as entrance buttons IlllNB, IUZNB, i03NB, IMNB, INB, IBSNB, llllNB, IQBNB, IGQNB, HONB and IHNB for the respective signals indicated by their preceding numerals. Also, an exit button X3 is provided for the exit end of each route, such as exit buttons IOIXB, IllZXB, 33KB, IMXB, KB, IUGXB, lillXB, IUBXB, IBSXB, HOXB and IIIXB for the routes endin at the signals indicated by the preceding numerals. It is to be understood, however, that the ends of the routes may or may not correspond to the locations of signals represented on the miniature track diagram, since a route is usually considered as extending from one particular signal to the next signal governing traffic in the same direction, but may extend to some arbitrarily chosen point where there is no signal, as at the end of territory under the control of the operator.

For the purpose of the disclosure of the present invention, each entrance button NB is considered to be in the form of a knob which is rotated 90 from a normal position to an operated position in which operated position it remains until manually restored. Each knob is provided with contacts which are closed when it is in the normal position and other contacts which are closed when it is in an operated position, such contacts being associated with their respective knobs in the disclosure by dotted lines. However, it is to be understood that various other types of manual control means may be employed, as will be mentioned more specifically hereinafter.

Each of the exit buttons X3 is of the self-restoring push button type, and has been indicated as associated with its contacts by a suitable dotted line. It is to be understood that the entrance and exit buttons may be associated on the control panel in accordance with any desired plan and still be within the scope of the present invention while accomplishing the novel control of routes by the distinctive actuation of buttons for each of the opposite ends of any route, without operating the individual elements or functions of the routes, through the medium of self-selecting networks organized according to the principles set forth herein.

The control machine also includes auxiliary switch control levers SML, which are associated with their respective switch machines SM as indicated by their preceding numerals, and of which only the lever BSML has been shown (see Fig. These emergency switch control levers may be suitably located on the control panel, or may be suitably located on the back of the control machine, as desired, inasmuch as these control levers are merely auxiliary levers for individually operating the levers under certain abnormal conditions hereinafter described in detail.

System devices-The entrance buttons NB and exit buttons K3 are respectively indicated as connected to the contacts which they operate by suitable dotted lines so as to make their relationships readily apparent. Each exit button XB has associated therewith an exit relay XR. Although the entrance buttons NB are shown as operating contacts directly included in the selfselecting networks of the system, it is to be understood that such control may be repeated through entrance relays, if it is so desired.

The contacts of the entrance button NB for one end of a route and the contacts of the exit relay XR for the opposite end of that route jointly control the positioning of the proper switch control relays for the switches and crossovers in that route.

For each crossover, switch control relays AN, R and EN is employed, while for each single switch, control relays N and R are employed. These relays are of the neutral type and govern the operation of their respective switch machines through the medium of polar-neutral retlays WZ as hereinafter described. These switch control relays AN, R, BN, N and R are selected through the self-selecting network of thesystem by certain auxiliary relays AZ and BZ and Z in a manner specifically described hereinafter.

With reference to Figs. 4 and 5, the relationships of these switch control and selecting relays may be more readily appreciated. The

crossover including the track switches 9TSA and QTSB are controlled by the switch machine 9SM, which switch machine is in turn controlled by the switch controlling relay 9WZ, while the switch control relays SAN, 9R and EBN control the relay 9WZ. It will be readily apparent that the relays 9AN and QBNare respectively associated with the switches BTSA and STSB, as the reference characters 9A and 9B are common to both sets of devices. Similarly, the selecting re- 1ays 9AZ and 9BZ are respectively associated with the switches BTSA and QTSB, as designated in their reference characters having their common characteristics 9A and 913. However, relay SR. is associated directly with both track switches STSAand BTSB.

Each track switch or crossover has associated therewith a lock relay L which prevents the 0peration of such track switch when it is unsafe for has been designated by the single relay BRL.

This route locking may include any suitable route locking features such as shown for example in the above mentioned application of S. N. Wight, Ser. No. 69,905, filed March 20, 1936, or

as shown in the patent of C, F. Stoltz, Patent No. 2,115,511 granted April 26, 1938, but it is believed unnecessary for an understanding of the use of route locking in the present invention to disclose the details of such locking.

Relays NOR and RCR are provided for each track switch or crossover to indicate when such track switch is in correspondence with its control relays, as will be pointed out in detail hereinafter.

A signal control relay G is provided for each signal for causing that signal to indicate clear or stop. These signal control relays have been specifically shown for each of the signals in the track layout and the selecting circuits for such relays have been shown in detail. However, the dotted lines connecting such relays with their respective signals have been omitted in all figures of the disclosure except where the association is made readily apparent in the usual conventional manner without adding complexity to the drawings, as in Fig. 8.

It is believed that the remaining features of the present invention will be best understood by considering the detailed operation of the system.

Operation It is believed expedient to first consider the invention with regard to its simplest form, that is. the embodiment of the invention which includes only a single interlocked group. The placing of Figs. 1 and 4 end to end shows the track diagram and self-selecting network for such a single interlocked group; while the placing of Figs. 6 and 3 end to end shows the actual track layout in the field together with the signal circuit selections for such layout.

Fig. 5 is used with this arrangement of drawings which shows a single interlocked group, and is also used with the arrangement of drawings which shows a plurality of groups combined for end-to-end operation, to show in detail a typical switch control carried from switch control relays of the self-selecting network to their switch machine. This control is typical of every track switch in the layout irrespective of whether there is but a single switch or whether there is a crossover involved.

Inasmuch as one form of the invention employs Figs. 1 and 4, for example, placed end to end, while another form of the invention employs these two Figs. 1 and 4 separated by Figs. 2 and 3, it becomes necessary to employ a special system of numbering of the wires which cross the sheets of drawings so as to readily identify the circuits as they are pointed out in detail. To accomplish this purpose, each wire mentioned as extending from Fig. l, for example, will be given a separate reference character such as wire 33 while this wire in extending to Fig. 2 will be given the reference character 33 but when mentioned in Fig. 4, it will be given the reference character 33*. In other words, when a circuit is traced with Figs. 1, 2, 3 and 4 used together, the reference characters will point out in which figures such wires may be found, although the base number will readily identify which wires fall opposite each other when Figs. 1 and 2 are placed end to end.

With this general organization in mind, we may now consider the operation of the system'in establishing a route through the track layout for the single interlocked group.

Normal conditions. Although the track switches TS are usually left in their last operated positions under normal operating conditions,

they have been shown in the disclosure in positions for the passage of main line traffic. The signals are considered to be normally at stop with the lower or red indicator of each signal normally illuminated, unless approach lighting features are employed in accordance with well known practices.

The track circuits are all unoccupied so that their respective track relays T are normally picked up.

All of the lock relays L are normally energized as will be readily apparent upon the consideration of the lock relay L of Fig. 5, which will be considered in detail hereinafter.

All of the switch control relays N, R and WZ are normally deenergized. It is preferable that all of the indicators on the control panel be normally deenergized to provide what has been conveniently termed a normally dark board, although any arrangement of indications may be employed with the present invention without departing from the use of the principles involved in the present invention.

Preselectton operation by a. SGZf SEZCCtiTLg initiattng circuit network-As previously explained, the operation of the system of this invention to select or establish a route involves what is conveniently termed a conditioning or preselection operation initiated by the operation of an entrance button alone, followed by a completion operation in response to the actuation of an exit button.

In the specific embodiment of the invention illustrated, the position of trailed single switches and ends of crossovers is preselected by the energized or non-energized condition of an associated pro-selecting relay Z, the energized condition of this relay corresponding to operation to the normal position, and the deenergized condition to the reverse position. Upon actuation of an entrance button, the appropriate pro-selecting relays Z for the switches, which are included in the various routes originatin at the corresponding entrance signal location and which are disposed in a trailed relation to said entrance signal location, are energized by circuit paths arranged in therform of a network. Since these switches of an interlocked group that are trailed for one direction of train movement, are in a facing point position for the opposite direction, there are separate initiating circuit networks for opposite directions of train movement over an interlocked group.

Considering a typical example of this preselection operation, let us consider that the operator desires to establish a route from the entrance signal IUI to the signal m8. To do this, he turns the entrance button IBINB clockwise to an operated position to close contacts 30 and apply electrical energy to a feed point of the initiating circuit network. This causes energization of a preselecting relay Z for each of the trailed switches required to be normal in all of the routes originating at the entrance signal ltd. In other words, theme-selecting relays Z of all of the switches, which are included in all the routes originating at signal iiii, receive energy over the circuit paths of the initiating circuit network, providing such switches are in a trailing relation to this entrance signal Bill, and also providing these switches are trailed in the normal position.

Applying these principles in the case of the assumed actuation of entrance button llliNB, it will be evident upon reference to the track laygut illustrated that there is one route from the signal iii! to signal I98, and'another route from A train moving from of the crossover 9; but since this switch is in the facing point relation to the signal HH, its pro-selecting relay 9AZ does not have its energization controlled. The switch STSB for the lower end of the crossover 9 is included in a trailing relation to the entrance signal lfll in the route to signal "39; but since this switch is trailed in the reverse position, its associated relay QBZ is left deenergized. The switch lfiTSA for the upper end of the crossover lil is in a trailing relation to the entrance signal NH and is included in the route to signal I08; and since this switch is trailed in the normal position, its associated relay IQAZ is energized over a circuit path of the initiating circuit network, which will be presently traced in detail. The switch IOTSB for the lower end of the crossover iii is included in the route to signal Hi9 but is in a facing point relation to the entrance signal liH, so that its relay HEBZ does not have its energization conrolled. The switch i ITS is included in the route to signal I89, and is also trailed in the normal position, so that its pre-selecting relay HZ is energized by a circuit path which will be presently traced in detail.

The circuits for energizing the pro-selecting relays ifiAZ and NZ in the example under consideration may be traced from through the contact 36 of the entrance button IMNB, back contact 3! of the exit relay IOIXR for the same signal location, back contact 32 of relay 32, wire 33 of Fig. 1 to vrire 33 of Fig. 4, where the circuit. divides into two branches for the energization of relays iEiAZ and NZ respectively. For the energization of relay IEPAZ the circuit continues through back contact 34 of relay 9R, back contact 35 of relay MR, winding of relay IUAZ to the energization of this relay IBAZ closing its front contact and continuing the circult to the exit relay itBXR. The branch circuit for energizing the relay HZ continues from wire 3 through the back contact 35 of relay SAN, back contact 253 of relay QBN, back contact 31 of relay 9BZ, back contact 38 of relay HER, back contact 39 of relay HR, winding of relay HZ to the energization of this relay HZ closing its front contact 93 to continue the circuit to the exit relay IGQXR.

These initiating circuit paths just traced exemplify certain characteristics or features of the initiating circuit network which may be discussed at this time. From one standpoint, the initiat= ing circuit network may be said to comprise wires or circuit portions arranged and interconnected through front and back contacts of the pro-selecting relays Z to conform with the track layout, in such a way that there is a complete initiating circuit for each route, usually comprising a piurality of such interconnected circuit portions, which are energized by the actuation of an entrance button for that route and which supply current for the energization of the exit relay of that route, when the exit button is operated. Each of these circuit portions, which may be considered as relating to either the normal or the reverse position of the associated ingle switch or end of a; crossover, includes a back. contact of the switch control relay for the other position of its switch, so that current may flow over the initiating circuit for a route only so far as there is a path available for train movement along that route not in conflict with some other route then established by the route establishing means, with the result that no current is supplied to energize an exit relay, unless some route can be established to the corresponding exit signal location from the entrance signal location designated. In other words, the initiating circuit network, in addition to providing for the energization of appropriate pre-selecting relays, serves to supply operating current to exit relays for rendering effective the manual actuation of exit buttons for routes not in conflict with established routes.

For example, in the case of the route from the signal I to signal I09, the circuit path above traced for energizing the pre-selecting relay IIZ to close its contact I98 and supplying an operating potential to the relay I09XR, includes the back contact 39 of the reverse switch control relay IIR, so that if there should be a route established over the switch II in its reverse position, the pro-selecting relay II Z cannot be energized to position this switch for operation to the normal position, and the exit relay I 09KB cannot be energized for any route over this switch in the normal position. Similarly, the energizing circuit for pro-selecting relay I IZ includes a back contact 38 of the reverse switch control relay IOR for the crossover I0, so that if this crossover is included in its reverse position in any established route, the pro-selecting relay HZ cannot be energized, nor current supplied to the exit relay I09XR. In this connection, it will be evident that if either switch I I or crossover I0 is included in the reverse position in some established route, no route can be established to the exit signal location I09.

In the case of the crossover 9, the route from signal IOI to signal I09 is over this crossover in the reverse position, and under these conditions, the circuit for energizing the pre-selecting relay I IZ includes the back contacts 250 and 36 respectively of the normal switch control relays 9BN and SAN for this crossover, so that if there is a route established over either end of this crossover in the normal position, the relay IIZ and the exit relay I09XR cannot be energized from entrance contact 30. In the case of the remaining switch 3, required to be in the reverse position for the route from signal IOI this signal I09 under consideration, and although the circuit for supplying current to the pro-selecting relay HZ may include a back contact of the relay 3N in the same way as in the case of the single switch IT, as illustrated in this particular instance, the back contact 32 of the relay 3Z is used to open said energizing circuit if the switch 3 is included in some route in its normal position, since the relay 3Z is energized when the switch 3 is controlled to its normal position for a conflicting route originating at the signal I02.

In a similar way and in accordance with the same principles, back contacts of the switch control relays are included in the various circuit paths for the energization of the pre-selecting relays Z of the initiating circuit network; and as will appear as initiating circuits for various routes are traced later. Upon operation of an entrance button to supply potential to a feed point of the initiating circuit network, no operating potential is supplied to an exit relay'unless some route can be established to the corresponding exit signal location from the entrance signal location designated, and each pre-selecting relay is energized only if a path for train movement is available from the designated entrance signal location to and over the corresponding switch in its normal position.

In connection with such a network arrangement of initiating circuit paths, the contacts of the Dre-selecting relays Z act to isolate circuit portions of the network and avoid the flow of current over circuit paths that would otherwise cause improper energization of pre-selecting relays 'for impossible routes and also supply current to exit relays when a possible route could not be established. For example, the front and back contact 32 ofthe pre-selecting relay 3Z iso-- lates the connections which supply current from the entrance buttons I 0INB and I02NB respectively to the wire or circuit portion 33. In other words, the circuit portion for the reverse position of switch 3 is disconnected from the circuit portion for the normal position of this switch, so that upon actuation of the button I 0INB, for example, current may not flow in a reverse direction, so to speak, over a circuit path correspondingto the crossover 2 in the reverse position and energize the pre-selecting relay 9BZ improperly, there being no possible route from the entrance signal IOI over the crossover 2 in the reverse position and the crossover 9 in the normal position. In short. the contacts of the pre-selecting relays Z may be said to limit the flow of current to initiating circuits for possible routes.

' Completion operation by a completion circuit networ7c.After the energization of the initiating circuit network in response to the actuation of an entrance button just described, resultingin preselecting the position of the trailed switches in all of the routes originating, at the corresponding entrance signal location, operation of the exit button for a particular one of these routes energizes the corresponding exit relay.

In the particular route under consideration, only the relay IOAZ is picked up although there may be other pre-selecting relays picked up for the other routes emanating from signal I0 I, such as relay I IZ. Upon the actuation of the exit button I08XB, a circuit is completed for energizing the relay I08XB from through a circuit including lever contacts 30 in an operated position, back contact 3i of relay IIIIXR, back contact 32 of relay 32, wire 33 wire 33*, back contact 34 of of relay 9R, back contact 35 of relay IOR, front contact 40 of relay IOAZ, windings of relay I08 Gt, back contact 4| of exit button I08XB, lever contact 42 of entrance button I 08NB in a normal position, to The current, which flows in this pick-up circuit, causes the contacts of the relay I08XB, to be picked up. The closure of contact 43 of relay I 08XR applies to the right hand terminal of relay I08XR to shunt out the self-restoring contact 4| of the exit button I08XB to thereby cause relay IGSXR to be stuck up dependent upon the entrance button IUINB, although the operator releases the exit button I08XB.

It will be noted that there is an auxiliary pick-up circuit for the exit relay I08XB. from through a circuit including lever contact 30 of entrance button IOINB in an operated position, back contact 3| of relay IOIXR, back contact 32 of relay 3Z, wire 33 wire 33 back contact 36 of relay SAN, back contact 250 of relay SEN; back contact '31 of relay= fiBZjiback contact 235 of: relay 'IUBN, back contact 239 of relay HLAN back contact l'll of 'relay IUAZ', windings of relay "IOBXR', back contact 4 of exitbutt'on lfiB-XB; lever contact 42 of entrance button HJ8NB in a normal position, to

This circuit-is-not closed under the usual-opicrating conditions because the relay l UAZis-immediately-picked up upon theclosure of the lever contact 30, and also because a short intervalzof time occurs between the operation of the entrancebutton IUINB and the operation ofthe exit button HIBXB; so that the relay IOAZ' has time to'pi'ck up and openthis auxiliary pick-up circuit iat back 'contact dfl'. However, if therelay l'IiA-Z. fails-to pick up either because of a. faultin its pick-up:- circuit or because it's pickup" circuit has been manually opened (as hereinafter pointed out), a so-called. run-around route will be established over the crossovers 9 and "Lin reverse positions; This run-around route will be discussed in detail following the consideration of the completion of the main route governed by the operation of the entrance button. HIIINB and the: exit button l OBXBl This 'energization of the exit relay HIBXR closes its: contact 44 and supplies an operating potential: to a. completion-circuit network which maybe said to-be analogous to the initiating circuit'network in the sense that it comprises wires or -circuit portions, corresponding to the normal or rever'se position of each single switch or end offa crossover, which are inte'r-c'onnected in accordancewiththe arrangement of the switches in the track layout, by front or back contacts of the-pre-selecting relays-Z, or by'front contacts of reverse switch control relays, or by direct connections, asthe case may be. Each of these circuit portions, corresponding respectively to the nor-mal or reverse sition of one of the track switches, has its associated normalor reverse switch control relay connected to it, so that the application-of an operating potential to such circuit portion effects the energization ofthe normal or reverse switch control relay to causeoperation of the track switch to a corresponding position. Upon energization of the initiating circuit network in response to the manual actuation of any given entrance contact, the resultant energized or non-energizedcondition of the pro-selecting relays serves in effect to connect the variouscircuit portions for the energization of switch control relays in such a way'that upon application of a potential to'a feed point of the completion circuit-network corresponding. to the exit end of a route, the proper normal or reverse switch control relays-for the switches or ends of crossovers-to establish that route'are energized.

In the arrangement illustrated, there is- -a completion circuit network for each directionof train movement through an interlocked group, and separate windings of' the switch control relays are energized 'by these completion circuit networks.

The-completion circuit network for a given di-- rectionmay be explained as 'acting to govern the position of successive switches in turn, starting with' the switch nearestthe exit-end, dependent upon the energized or non-energized condition of the associated pro-selecting relay Z'in the case of" aiswitch in a trailing relation to the entrance end; or in accordance with the circuit connections of thenetwork" in thecase of theremaining switches in the route disposed in a trailingrelation to the exit end. In. other words, the circuit connections of the completion circuit network existing after the pro-selection operation may be considered as acting to energize the switch: control relays of successive switches, starting with thoseinearest the exit end, to build up'a route by'the action of current passing along circuitportions of the completion circuit network in much the same way as a train would do infollowing: a path backward from the exit signal' location toward the entrance signal location overtswitches in their pro-selected position.

Considering atypical example of this completionioperation for the route from the signal [0| and'xsignal I08, when the exit relay IBSXR, is energized and closes its contact 44, an operating potential is applied to a feed point of the completion circuit'network corresponding to this exit signal location. The switch IUTSA for the upper end of the crossover. I0 is the switch nearest'this exit end; and since it is in trailing relation to the entrance signal I8 I its position is determined bythe condition of the pre-selecting relay IBAZ. Astpreviously' explained, this relay IGAZ is energized by theinitiating circuit, and hence the wire or circuit portion to which current is applied through the front contact E4 of the exit relay l ilfiimis connected through the front contact 45 of the relay lilAZ to the circuit portion of the network which corresponds with the normal position of thisswitch IGTSA, and to which is connected the normal switch control relay IUAN, so that the relay IOAN is energized by a circuit which may be traced from through front contact 44 of relay" IQ8XR, front contact 45 of relay IUAZ, winding of relay 'lllAN, through back contact of' relay IOAZ', winding of relay IAN, through back contact 46"0f relay HER, to

It having thus been determined that the route to bebuilt up is over the upper end of the crossover It! in its normal position and along the upper track, it can. be seen upon referring to the track layout that,.if this upper end of the crossover is: to be in. the normal position for a route, the switch STSA for the upper end of the crossover- 9'must also be in the normal position; and hence the. circuit portions for the relays SAN and JAN may be directly connected. In other words, the position of the switch BTSA, which is disposed in a trailing relation to the exit end, is determined when the positioning of the switch l-UTSA is' determined; and there is only one position whichv the switch STSA may have to provide a path for train movement, so that relay BAN may be energized in multiple with relay IOAN by a circuit readily traced through the upper winding of relay 9AN and back contact 41 of relay SE, to

The positioning of the switch IElTSA for the upper end of the crossover [0 in accordance with its preselection also determines that the route to be established is along the upper track, and accordingly current is passed on from the wire energizing relay IOAN through back contact 48 of relay'fiR to wire 49 of Fig. 4 connected to wire 49 0f. Fig. 1 and to the contact 56 of the preselecting relay 3Z for the next succeeding switch 3. Switch 3. is in a trailing relation to the entrance-signal llll, but is trailed in the reverse position, and hence its pre-selecting relay 3Z is not energized. Current is thus supplied through the back contact 59 of this relay 3Z to the circuit portion for the reverse position of this switch, to which is connected the reverse switch control relay"3R',-so that its upper winding is energized by a circuit readily trace'dfrom through front contact 44 of re'laylflBXR, front contact -45 of relay IOAZ, back contact 48 of relay 9R, wires 49 and 49 back contact 50 of relay 3Z, upper winding of relay 3R, back contact 5| of relay 3N, to

In connectionwith the completion circuit network, it may be pointed out here that certain circuit portions thereof are connected upon energization of reverse switch control relays, and other connections normally existing are broken upon-such energization. For example, in the case of the route from signal It! to we just described, the circuit portions for the energization of relays'SAN is normally connectedthrough the back contact 48 of the reverse switch control relay SE to the wire 49 leading to the contactEU of the pre-selecting relay 3Z, while the-circuit path for the energization of the reverse switch control relay 9R is connected to the wire 49 through its front contact 48. This arrangement of interconnecting circuit portions of the completion circuit networkthrough front and back contacts of reverse switch control relays'is employed for the purpose of isolating the circuit portions for the energization of normal and reverse switch control relays, so that current supplied to a reverse switch control relay of a switch cannot also flow to a normal switch control relay of that switch and any associated switch, or vice versa, and thereby cause the undesired operation of switch-control relays.

Considering another characteristic of the-completion circuit network, the operation of an entrance button energizes pre-selecting relays for all of the establishable routes originating at the corresponding entrance signal location; and when a particular one of these routes is established by the operation of the completion circuit network, the pre-selection is rendered ineffective with respect to all of the otherroutes originating at the same'entrance signal location. For example, at the time the exit relay ltSXR is energized' and the route of signal Hil to signal IE8 is established as just described, other initiating circuit paths are energized to energize pre-selecting relay HZ for a route from signal Hi! to signal I89; and when the route from signal liil to signal W8 is established, these other'initiating circuit paths for the other routes are broken soas to prevent energization of relay HZ so far as its energization from the entrance button IEHNB is concerned, but at the same time leave available initiating circuit paths for the energization of the pre-selecting relay HZ upon actuation of some other entrance button for a non-conflicting route, such as the'entrance button HESNB. This effect is produced by opening theback contact 36 of switch control relay 9AN, whenthe upper end of the crossover 9 is operated to the normal position, to interrupt the supply of current to the relay HZ from the button IOlNB, this being the point of conflict between the established route from signal it! to signal Hi8 and the route from signal Illl to signal I09. It can be seen that the opening of this back contact 36 of the switch control relay SAN does not prevent the energization of relay HZ upon'the operation of some other entrance button, such as entrance button IHZSNB, for some route not in conflict with the established route, such as over the lower end of the crossover 9 in the normal position. Thesame plan of control applies to the other routes; and it may be said that uponestablishing a given route, the initiating circuit paths for all other all) routes originating :at the same entrance signal location are interrupted .at the points of. conflict.

Furthenthe energization of switch control relays to establish a route controls the circuits in such a way that the operation of an entrance and/or exit button for any conflicting route will not effect any change in the circuits of the initiating and completion circuit network so far as the established route is concerned. This interlock betweenconflicting routes will be considered later in detail, and it is considered expedient to discussnow the manner in which the switch control relays govern the operation of their associated track switches.

From the above description, it will be seen that the operation of an entrance button NB closes a contact which applies positive potential to what are conveniently termed initiating circuit paths which correspond to the available routes emanating from the entrance point corresponding to the operated entrance button. The operation of the exit button XB employs the energy of a particular one of the initiating circuittpaths-to pick up and stick the exit relay for the corresponding exit point, which exit relay applies energy to a completion circuit path corresponding to the initiating circuit path supplying energy to such exit relay. It will, of course, be apparent that only one completion circuit path can be energized by the picking up of an exit relay because the preselecting relays Z allow energy to be applied only to the completion circuit path corresponding to the employed initiating circuit path, and the response of the N and R relays to the energization of the completion circuit paths completely .isolates the initiating and completion circuit paths sothat they can not be interrupted by .theoperation of an entrance and exit button for a conflicting route.

In general, it may be stated that there is a group ofinitiating circuit paths for each direction and a group of completion'circuit paths for each. direction with the circuits of each group arranged according to theseveral routes through the track layout, and the initiating and completion'circuit paths for each route cooperate to establish that route to which they correspond. These principles apply both to the simplified track layout arrangement of Figs. 1 and 4 and also to the more-complex track layout'arrangement of Figs. 1, 2, 3 and l. vIn other words, the principles of the self-selecting network of the present invention are applicable both within a single interlockedfgroup and also to a number of related interlocked .groups, all of which will be more clearly apparent as the system of the pres ent invention is further discussed.

Switch control.Each of the track switches included in the route respond to their respective switch control relaysfN and R, but only the operation with respect to the control of the crossover t! will-be described in detail with reference to Fig. 5, as control is typical of theloperation of all of the track switches.

More specifically, the switch control relaynQAN has been picked up by the operation of the selfselecting network. This closes an energizing circuit for the switch control relay tWZ from through-a circuit including front contact 57 of relay ISAN, front contact 58 of relay 5L, upper winding of relay 5W2, to The energy which flows in this circuit actuates the polar contacts of the relay EWZ to right-hand positions and causes the neutral contacts to be picked-up.

The response of the relay 9W2 closes the normal operating circuit for the switch machine 9SM from through a circuit including front contact 59 of relay 9WZ, polar contact 60 of relay 9WZ in a right hand position, front contact 6| of lock relay 9L, through the switch machine 95M, front contact 62 of lock relay 9L, polar contact 53 of relay QWZ in a right hand position, to"(-). The current which flows in this normal operating circuit causes the switch machine SSM to operate the track switches QTSA and STSB to normal positions, if they are not already in such position.

It will be noted that the normal energizing circuit for the relay QWZ and also the operating circuit for the switch machine 9SM include front contacts 58 and BI respectively of the lock relay 9L. This lock relay 9L is normally energized by a circuit closed at through a circuit including front contact 64 of route locking relay 9RL, front contact 65 of relay HT, front contact 66 of relay I8T, back contact 61 of relay SWZ, windings of relay 9L, to

The energization of the relay 9W2 opens this pick-up circuit for the lock relay 9L at back contact 61, so that, when the switch machine SSM is already in a normal position, as in the case under consideration, the correspondence relay BNCR, is already energized, which allows the lock relay 9L to immediately drop away.

The energizing circuit for the normal correspondence relay BNCR is closed from through a circuit including polar contact 68 of relay 9WZ in a right-hand position, windings of relay SNCR, polar contact 69 of relay SWP in a right-hand position, front contact 19 of relay 9WP, back contact H of relay SE. to

On the other hand, if the track switches STSA and STSB were in reverse positions before the switch control relay SAN is picked up, then the reverse correspondence relay would be energized. Such energizing circuit for the relay QRCR. would be closed from through a circuit including polar contact 68 in a left-hand position, windings of relay HRCR, polar contact 12 of relay QWP in a left-hand position, front contact 13 of relay 9WP, back contact 14 of relay 9BN, back contact 15 of relay 9AN, to

Under such circumstances, the picking up of the relay SAN opens back contact 15 deenergizing the relay QRCR. The actuation of the polar contact 68 of relay SWZ to a right-hand position continues to cause the deenergization of the relay SRCR, and the normal correspondence relay SNCR is not picked up until the track switches BTSA and STSB are completely operated to normal positions. Thus, upon the opening of back contact 61 of relay 9WZ, a stick circuit is closed for the lock relay from through a circuit including front contact 64 of route locking relay 9RL, front cotnact 65 of relay l'lT, front contact 66 of relay I8T, back contact 16 of relay QNCR, back contact 11 of relay 9RCR, front contact 18 of relay 9L, windings of relay 9L, to

This stick circuit maintains the relay 9L energized until the track switches STSA and QTSB are operated into correspondence with the switch control relays 9WZ, HAN, SR. and SNB at which time the relay SNCR is picked up opening back contact 16 and 'deenergizing relay 9L, preventing further control of switch control relay SWZ. It is noted that the lock relay 9L is made slightly slow acting so as to bridge any time period between the opening of back contact 61 of relay BWZ and the closing of either of the contacts 16 of relay QNCR or '11 of relay IRCR depending upon which operation of the switch machine is to occur.

The dropping away of the lock relay 9L causes the switch control 9W2 to be maintained energized through a stick circuit closed from through a circuit including front contact 5'! of relay 9AN, back contact 53 of lock relay 9L, polar contact 79 of relay 9W2 in a right hand position, upper winding of relay SWZ, to It is to be understood that the relay SWZ is sufficiently slow acting to bridge the gap of energization between the opening of front contact 58 of relay 9L and the closing of back contact 58 so as to be continuously picked up during the drop away of the lock relay 9L. 7

If the switch control relay SAN is deenergized for some reason before the switch machine 9SM completes the operation of the track switches HTSA and STSB to proper positions, a stick circuit is closed for the relay 9WZ to maintain it energized for the completion of the switch machine stroke. This circuit is closed from through a circuit including back contact 80 of relay SWP, front contact 8| of relay 9WZ, polar contact 19 of relay -9WZ in a right hand position to energize the upper winding of relay 9WZ when it has been actuated to a normal controlling position, and in a left hand position to energize the lower winding of the relay 9W2 when it has been actuated to a reverse controlling position, to It is of course understood that the relay 9WP is deenergized whenever the track switches BTSA and STSB are being operated from one position to another, and also that the correspondence relays QRCR and BNCR are deenergized by reason of open front contacts Hi and 13 thereby causing the lock relay 9L to be maintained energized.

Before continuing with the completion of the route under consideration at this time, let us observe the manner in which the reverse operation of the track switches STSA and STSB is prevented while the route is locked either by the presence of a train on the track circuit I8T or upon the deenergization of the route locking relay RL. While the route is locked in advance of a train or is occupied by a train, the lock relay 9L is maintained denergized. Under such conditions, the operator might, through operations later to be considered, cause the picking up of the reverse switch controlling relay 9R which would deenergize the normal correspondence relay 9NCR at open back contact I I, but the lock relay 9L is dropped away so that energy is merely applied to the stick circuit for the relay SWZ from through a circuit including front contact 82 of relay 9R, back contact 83 of relay 9L, polar contact 19 of relay SWZ in a right hand position, upper winding of relay SWZ, to Such energization of the relay 9WZ merely maintains its polar contacts in their former right hand positions and maintains its neutral contacts picked up.

If a momentary loss of shunt should occur causing the pick-up circuit of the lock relay 9L to be closed at front contact 66 of relay IBT, the pick-up circuit of the lock relay 9L would not be energized because of opened back contact 61 of relay 9W2 which is maintained energized by its stick circuit.

In order for the reverse operation of the track switches to be accomplished (or any operation to an opposite position), all of the switch control- 

